Double solenoid with interlock

ABSTRACT

A double solenoid electrical switching device comprises a pair of solenoid switches mounted together on a common base, the plungers of which are spaced from each other by a longitudinally movable interlock pin having a length which is such that when the contacts of one of the solenoids are closed, the pin is moved by the plunger of that solenoid to a position in which the plunger of the other solenoid is prevented from moving so as to simultaneously close its contact.

United States Patent 1 1 [111 3,716,811 Prouty et al. 1 Feb. 13, 1973 [541 DOUBLE SOLENOID WITH 3,312,122 4/1967 Conner et al ..335/160 INTERLOCK 3,536,868 10/1970 Lawrence et al ....3 35/160 2,396,972 3/1946 Russell ....335/159 Inventors: Robert y, g p 2,52l,969 9/1950 Dugan ..335/161 Assignee: {E s x International, n Wayne, Attorne 'y-Molinare,Ailegretti,Newitt& Witcoff n 1 [22] Filed: Sept. 20, 1971 [57] ABSTRACT [2]] Appl. No.: 182,015 A double solenoid electrical switching device comprises a pair of solenoid switches mounted together on Y a common base, the plungers of which are spaced from each other by a longitudinally movable interlock [58] Fieid 162 259 pin having a length which is such that when the con- 335/262 2551200) tacts of one of the solenoids are closed, thev pin is moved by the plunger of that solenoid to a position in [56] References Cited which the plunger of the other solenoid isprevented from moving so as to simultaneously close its contact. UNITED STATES PATENTS 10 Claims, 1 Drawing Figure 1,819,061 8/l93l Bancroft ..335/l60 1 Robert I). Graf, Flora, both of Ind.

Primary Examiner-Harold Broome DOUBLE SOLENOID WITH INTERLOCK BACKGROUND OF THE INVENTION This invention relates to a double solenoid switching device and, more particularly, to a double solenoid electrical switching device having an interlock which prevents the simultaneous operation of the electrical contacts of the respective solenoids.

Electrical switching systems having two or more solenoids are frequently employed in single or two field electrical motors in which multiple speed, reversing, dynamic braking or more than one of those features is desired. Such motors find application in cranes, electrically driven tractors and trucks, and the like. In such multiple field motor applications, burnout of the motor fields'due to the simultaneous energization of the fields is an important consideration, since it is obvious that such burnout will result in expensive repairs, as well as down time. Burnout is a constant threat where double independently operating solenoids are provided for the selective actuation of the separate motor fields, since simultaneous actuation of both such independent solenoids is possible. In addition, the solenoid contacts tend to tack weld, particularly in large installations where initial current flows are high, and, if the contacts of one of the field circuits become so welded and the other circuit is energized, burnout will result.

In order to avoid burnout of such motors, double solenoid electrical switching devices have been employed which utilize elaborate and complex flange, washer and spring assemblies as an interlock between the solenoids to prevent simultaneous operation of the respective solenoid contacts. One such prior double acting solenoid interlock takes the form of a set of flanges which are mounted to the respective solenoid plungers and are positioned so as to tensively restrain the movement of the plunger of one of the solenoids when the other plunger is actuated. Such tensive interlocks, however, are both complex in construction, large, and do not satisfactorily break previously tack welded contacts which have welded as a result of high current flows.

The double solenoid switching device incorporating the principles of the present invention is not only extremely simple and inexpensive in construction, but also is reliable and positively prevents motor burnout which might result from the simultaneous closing of the contacts of the respective solenoids. In the double solenoid electrical switching device incorporating the principles of the present invention, a simpleand inexpensive interlock not only positively and directly prevents simultaneous actuation of the respective contacts of the solenoids, but also is capable of breaking contacts which have become tack welded in operation and in the event that the weld remains unbroken, prevents further closing of the unwelded contacts.

SUMMARY OF THE INVENTION In a principal aspect, the double solenoid electrical switching device incorporating the principles of the present invention includes a pair of solenoid electrical contact switching assemblies in which surfaces on the respective contact carrying plungers of each of the solenoids are spaced from each other in the direction of their longitudinal movement by predetermined maximum and minimum distances and elongate means is mounted for contact with and is longitudinally movable between the plunger surfaces in response to movement of the plungers. The elongate means is of a length less than the predetermined maximum: distance between the plunger surfaces, but greater than the predetermined minimum distance whereby the elongate means prevents the surfaces of the plungers from being spaced from each other by the predetermined minimum distance and prevents the simultaneous actuation of the contacts of both solenoids.

In another principal aspect of the invention, the elongate means comprises a non-magnetizable pin which is longitudinally movable by contact with the plunger ends along an axis parallel to the axis of movement of the plungers.

These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWING In the course of this description, reference will frequently be made to the attached drawing in which the sole FIGURE thereof is a plan cross sectioned view of a preferred embodiment of double acting solenoid switching device constructed in accordance with the principles of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the drawing, a preferred embodiment of double solenoid with interlock is shown which comprises a pair of solenoid switching assemblies 1 and 1. Since both of the assemblies are substantially identical in construction to each other, the components of assembly l which correspond to identical components in assembly l will be designated by like reference nu.- merals which will be primed.

Each of the assemblies 1, 1' comprises a solenoid housing 2, 2' which is mounted, as by bolts 3 to a common base 4. The common base 4 may, in turn, carry suitable affixation apertures 5 for attachment of the double solenoid housings of the present invention to a suitable mounting panel or other foundation (not shown). It will be understood that instead of mounting the respective solenoid housings 2, 2' by way of the common base 4 shown in the drawing, the housings may be attached together by any other suitable means, such as a single integral housing, so long as the solenoid assemblies 1 and I are attached in a manner to provide for the joint interlock operation as will be later described.

Each of the solenoid housings 2, 2' contain a conventional solenoid actuating coil 6, 6' and a magnetizable solenoid plunger 8, 8' which is longitudinally movable within the respective coils. In addition, stationary contacts 10, ll, 10' 11' are also positioned within the housings and electrically communicate through the housings by way of suitable external terminals l2, l3, l2 and 13' respectively. A corresponding conductive movable contact 14, 14' is carried on one end of the plunger 8, 8' and is positioned so as to be movable into and out of electrical contact with the stationary contacts 10, ll, 10, 11' in response to movement of the plunger which, in turn, is responsive to actuation and deactuation of the coil 6, 6' so as to make and break a circuit between terminals 12, 13, 12', 13'. in the embodiment shown, normally open solenoid contacts are provided'in which the movable contacts l4, 14' are normally urged to the open position shown in solid in the drawing by a suitable spring l6, l6 and are closed upon energization of the coil 6, 6' which magnetically draws the magnetizable plunger 8, 8' into the coil and overcomes the force exerted by the spring.

The interlock assembly of the present invention will now be described. The interlock assembly 18 comprises a pair of stop members 20, 20 in the form of plugs which are stationarily mounted within the coil 6, 6' of each of the solenoids. An axial bore 22 extends longitudinally through the plugs 20, 20 and an elongate pin 24 is positioned in the bore 22. The diameter of the pin 24 is slightly less than that of the bore such that the pin is reciprocally movable in the bore and the pin is longer than the bore suchthat at least one end 26, 26' of the pin will extend from the bore at all times. The pin 24 may be formed of any suitable non-magnetizable material, stainless steel being preferred. The pin is selected to be of a length which is less than the longitudinal'distance between the plunger ends or impacting surfaces 28, 28' when the contacts 14, 14' of both plungers are opened. However, the length is greater than the distance which would obtain between the plunger impacting surfaces or ends 28, 28' if the contacts 14, 14' of both plungers could be simultaneously closed. Thus, the pin 24 will act to prevent such simultaneous closing of thecontacts as will be fully understood when considering the description of the operation which will follow.

Prior to describing the operation of the double solenoid switching device of the present invention, an exemplary circuit has been shown in the drawing in which the present invention may be employed. Such circuit, for example, might comprise a suitable source of power 30 for supplying electrical power to the forward and reverse field windings, for example 31 and 32, of an electrical motor 33 by way of terminals l2, l3 and 12', 13' respectively. In addition, power source 30 also supplies a control switch 34, the stationary contacts 36, 36' of which, in turn, may be contacted selectively by movable contact 38 to selectively energize or deenergize coils 6, 6.

In operation, it will first be assumed that the movable contact 38 of control switch 34 is in the neutral deenergizing position shown in solid in the drawing and the respective coils 6 and 6' are deenergized. When these coils are deenergized, their plungers 8, 8' will be urged by springs 16, 16 to the position shown in solid in the drawing so as to open their respective contacts 10, ll, 14 and 11', 14' and the interlock pin 24 will be positioned as shown in solid inthe drawing.

If it is now desired to operate the motor 33, for example in the forward direction, the movable contact 38 will be moved so as to contact stationary contact 36 and energize coil 6. When coil 6 is energized, the force exerted by spring 16 will be overcome and plunger 8 will move to the right to the position shown in dot and dash lines. In this position, the movable contact 14 will contact stationary contacts 10 and 11 so as to complete a circuit between terminals 12 and 13 to the forward field winding 31 of the motor 33. It will be seen from the drawing that when contacts l0, 11, 14 are closed, the end 28 of the plunger 8 will have moved to a position adjacent, but not necessarily in contact with the end 40 of the stop member 20 and will have impactingly struck the end 26 of pin 24 urging the pin to the right such that the other end 26' of the pin is positioned as shown in the dot and dash lines in the drawlf plunger 8' is now subjected to a force which might cause its movable contact 14' to move in a direction so as to close the circuit through terminals 12', 13' while the circuit through terminals 12 and 13 is closed, such closing will be prevented by contact of plunger end 28' with the end 26' of the inter-lock pin 24 before contacts 10, 11, 14' close. Such forces on plunger 8' might result due to the accidental energization of coil 6' or due to vibrational or other inertial forces exerted on plunger 8' which might overcome the force exerted by spring 16'. Preventative contact between the pin ends and the plunger ends is insured by selection of the length of the pin 24 such that it is less than the maximum distance which obtains between the ends 26 and 26' of the plungers when both of their respective contacts 14, 14' are open, but that the length is greater than the minimum distance which might otherwise obtain between the plunger ends if both contacts l4, 14 are simultaneously closed.

If it is now desired to either reverse the motor 33 or to brake the forward motion of the motor by deenergizing the forward field winding 31 and energizing the reverse field winding 32, movable contact 38 is simply reversed so as to break contact with contact 36 and make contact with contact 36', deenergizing coil 6 and energizing coil 6'. When coil 6 is deenergized, spring 16 will urge contacts 10, ll, 14 open, and when coil 6' is energized, plunger 8' will move to the left as viewed in the drawing, so as to close contacts 10, 11', 14' and urge the interlock pin 24 to the left so as to prevent reclosing of contacts 10, ll, 14. it will be seen that, if for some reason contacts 10, ll, 14 had become tack welded shut, simultaneous energization of the contacts 14, 14' will still be prevented by pin 24. In the event that contacts l0, l1, 14 are welded shut, the striking action on the pin 24 which is exerted by the impacting surface end 28 of plunger 8' as it moves to the left will usually be sufficient to break the weld and open contacts l0, l1, 14. Even if this striking force is not sufficient to break the weld, contacts 10', 11', 14' still will be prevented from closing by the blocking action of the interlock pin 24 and will thus prevent burnout of the usually expensive motor 33.

It should be understood that the embodiment of the present invention which has been described is merely illustrative of an application of the principles of the invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention.

What is claimed is 1. in a double solenoid electrical switching device having'a pair of plungers, a coil associated with each of said plungers for selectively moving each said plunger longitudinally in response to the energization of its coil, first and second contact means respectively associated with each of said plungers and adapted to open and close first andsecond electrical circuits in response to movement of their respective plungers, wherein the improvement comprises in combination therewith:

surfaces on each of said plungers being spaced from each other in the direction of their longitudinal movement by predetermined maximum and minimum distances, and elongate means mounted for contact with and longitudinal movement between said surfaces in response to the movement of said plungers, said elongate means having a length less than said predetermined maximum distance between said surfaces, but greater than said predetermined minimum distance, whereby said elongate means prevents said plunger surfaces from being spaced from each other by said predetermined minimum distance. v

2. In the device of claim 1 wherein said elongate means comprises a pin the ends of which are positioned to contact the ends of said plungers.

3. In the device of claim 1 wherein said elongate means comprises a non-magnetizable pin.

4. In the device of claim 1 wherein said elongate means and said plungers are longitudinally movable along axes parallel to each other.

5. In the device of claim 4 wherein said elongate means and at least one of said plungers are longitudinally movable along a common axis.

6. [n the device of claim 5 wherein said elongate means is a pin.

7. In the device of claim 1 including stop means positioned between the ends of each of said plungers, an elongate bore extending through said stop means, and a pin extending through and longitudinally movable in said bore and having a length greater than said bore, whereby said pin extends from at least one end of said bore and prevents simultaneous actuation of said firs and second contact means.

8. In the device of claim 7 wherein said plungers and said pin are longitudinally movable along a common ans.

9. In the device of claim 1 wherein when said first and second contact means are opened the distance between the surfaces of said plungers is greater than the length of said elongate means and when one of said contact means is closed one end of said elongate means is contacted by said surface of the plunger of said closed contact means and the other end of said elongate means is longitudinally moved to a position wherein said other end of said elongate means will contact said surface of the other plunger before its contact means closes, whereby simultaneous closing of said first and second contact means is prevented.

10. [n the device of claim 9 wherein said elongate means comprises a non-magnetizable pin, said pin and said plungers being movable along axes parallel to each other and said plunger surface comprises the ends of said plungers. 

1. In a double solenoid electrical switching device having a pair of plungers, a coil associated with each of said plungers for selectively moving each said plunger longitudinally in response to the energization of its coil, first and second contact means respectively associated with each of said plungers and adapted to open and close first and second electrical circuits in response to movement of their respective plungers, wherein the improvement comprises in combination therewith: surfaces on each of said plungers being spaced from each other in the direction of their longitudinal movement by predetermined maximum and minimum distances, and elongate means mounted for contact with and longitudinal movement between said surfaces in response to the movement of said plungers, said elongate means having a length less than said predetermined maximum distance between said surfaces, but greater than said predetermined minimum distance, whereby said elongate means prevents said plunger surfaces from being spaced from each other by said predetermined minimum distance.
 1. In a double solenoid electrical switching device having a pair of plungers, a coil associated with each of said plungers for selectively moving each said plunger longitudinally in response to the energization of its coil, first and second contact means respectively associated with each of said plungers and adapted to open and close first and second electrical circuits in response to movement of their respective plungers, wherein the improvement comprises in combination therewith: surfaces on each of said plungers being spaced from each other in the direction of their longitudinal movement by predetermined maximum and minimum distances, and elongate means mounted for contact with and longitudinal movement between said surfaces in response to the movement of said plungers, said elongate means having a length less than said predetermined maximum distance between said surfaces, but greater than said predetermined minimum distance, whereby said elongate means prevents said plunger surfaces from being spaced from each other by said predetermined minimum distance.
 2. In the device of claim 1 wherein said elongate means comprises a pin the ends of which are positioned to contact the ends of said plungers.
 3. In the device of claim 1 wherein said elongate means comprises a non-magnetizable pin.
 4. In the device of claim 1 wherein said elongate means and said plungers are longitudinally movable along axes parallel to each other.
 5. In the device of claim 4 wherein said elongate means and at least one of said plungers are longitudinally movable along a common axis.
 6. In the device of claim 5 wherein said elongate means is a pin.
 7. In the device of claim 1 including stop means positioned between the ends of each of said plungers, an elongate bore extending thRough said stop means, and a pin extending through and longitudinally movable in said bore and having a length greater than said bore, whereby said pin extends from at least one end of said bore and prevents simultaneous actuation of said first and second contact means.
 8. In the device of claim 7 wherein said plungers and said pin are longitudinally movable along a common axis.
 9. In the device of claim 1 wherein when said first and second contact means are opened the distance between the surfaces of said plungers is greater than the length of said elongate means and when one of said contact means is closed one end of said elongate means is contacted by said surface of the plunger of said closed contact means and the other end of said elongate means is longitudinally moved to a position wherein said other end of said elongate means will contact said surface of the other plunger before its contact means closes, whereby simultaneous closing of said first and second contact means is prevented. 